Yep, that is how it is done, but the demo is a circular vase. Some people call them daisy wheels. The circular/ring pots I have seen in Europe were used as a water jug by workers in the field. They were worn on the arm and a bit bigger than the one in the demo.
I don't know the use of the ones from Japan. Maybe John Baymore knows.

I just call it throwing a round tube without using an extruder. Largest I threw before was about 22" across and 6" in diameter. you can also extrude a tube and match it to a circle ... but meh ... I can throw a tube in 2 minutes, trimmed in 4 to 6 when dry enough.

Simple trick. just takes some practice making it, but much easier than learning how to throw a plate.

I call it a double walled pot. I have thrown smaller ones than 22" more in the range of 8-12 inches. They are a fun thing to do every so often.
Students get a kick out of it.

I find it interesting that they were worn on the arm as water jugs for peasants working in the fields. I have seen them made by contemporary potters in Spain and in archaeological museum all over Europe. They seem to be pretty universal.

Students do get a kick out of it. As a dare I made a chain out of them (pushed them into ovals then interlinked them) ... stretched it out about 85 feet and suspended between the second floor balcony railings ... was awesome to see hanging.